There are various types of carabiners for mountaineering and climbing. One such type includes those utilizing ring nuts, usable in particular for hooking a harness. Another type includes lever or wire carabiners which are normally used for quickdraws. In all cases, carabiners must be resistant to accidental opening, in particular when the carabiner is under load, such as in the case of a fall. In fact, when carabiners are under load, many forms of deformation may occur with the risk of creating non-optimal coupling between the mobile end of the closing element and the point of contact thereof with the coupling portion of the ring.
In order to reduce these drawbacks, carabiners are used which include a sort of hook that engages the end of the lever. While this solution increases the safety of the climber, the hook can interfere with movement of the rope thereby making extraction from the carabiner difficult during some phases of the climb.
The so-called “key-lock” fixing system shapes the end of the coupling ring as a T according to a cross section with respect to the plane in which the carabiner lies. The lever consequently has a coupling head of complementary shape, so as to achieve a shape coupling. This fastening system prevents the hook effect of conventional lever carabiners and ensures an acceptable level of safety against accidental opening, even if the risk of opening is still not averted.